Heat and pressure consolidated decorative laminates have historically been prepared from a core material comprising a plurality of phenolic resin impregnated kraft paper sheets, a face sheet impregnated with a melamine-formaldehyde resin and optionally a melamine resin impregnated overlay sheet. Such high pressure laminates have been used world-wide as construction materials for wall panels and countertops.
Decorative laminates having melamine-formaldehyde and polyester impregnated core sheets have recently been reported. Such laminates offer several distinct advantages over those in which a phenolic-based core material is employed. Most notably, the color of the core of the laminate matches that of the face or decor sheet. As a result, the dark edge line that is perceptible when conventional laminates are cut, is eliminated.
For instance, in U.S. Pat. No. 4,448,849 a melamine-formaldehyde resin containing a hydroxylmelamine is disclosed for impregnating core sheets and/or the decor sheet and/or the overlay sheet to provide a laminate with a solid color edge matching that of the core surface. Further, in U.S. Pat. No. 4,741,968, a laminate is disclosed wherein a polyester comprising the reaction product of a polyhydric alcohol, saturated dicarboxylic acid and unsaturated dicarboxylic acid is impregnated in the core sheet. The polyester impregnated core sheet offers distinct advantages over laminates containing a core sheet impregnated with melamine formaldehyde. In addition to being more tear resistant, the polyester impregnated core sheet containing laminates are characterized by greater flexibility, machinability, and punchability than laminates containing a melamine formaldehyde impregnated core sheet. In addition, the polyester impregnated core sheet containing laminates are less resistant to crazing than laminates containing melamine-formaldehyde, as evidenced by cracking tests. Unfortunately, the polyester containing laminates are unable to exhibit the high level of heat resistance exhibited by laminates containing a melamine formaldehyde impregnated core sheet.